Not Applicable.
This invention relates generally to antennas and more particularly to an antenna element and an antenna array that can operate in two or more frequency bands.
A variety of conventional antennas are used to provide operation over selected frequency regions of the radio frequency (RF) frequency band. Notably, stacked patch antenna arrays have been used to provide simultaneous operation in two or more RF frequency bands. Antenna array arrangements operating in two or more RF frequency bands can require complex mechanism and techniques to allow arrangements to be selectively tuned to the two or more frequency bands.
Existing stacked patch antenna elements that have been adapted to operated in two RF frequency bands sometimes use air gaps disposed between dielectric layers to tune each of the frequency bands. This technique provides dual-band stacked patch antenna elements for which fine tuning is very difficult. The technique also provides antenna elements that can achieve only a relatively small difference in the frequency between each of the two frequency bands. In contrast, some applications, for example global positioning system (GPS) applications, have two operating frequencies (designated herein as L1 and L2) that have relatively wide separation.
It will be recognized that a conventional GPS system provides L1 at 1575.42 MHz and L2 at 1227.60 MHz, each having a bandwidth of 24 MHz. An antenna that can provide a relatively large frequency separation is desirable.
Conventional antenna arrays are provided having a plurality of antenna elements. Coupling between respective ones of the plurality of elements can produce undesired antenna and system effects, for example, unwanted beam pattern behavior, and unwanted coupling between transmitting and receiving elements. Thus, it is desirable in an antenna array having a plurality of antenna elements to reduce the amount of coupling between respective ones of the plurality of antenna elements.
For GPS applications, microstrip antenna arrays have been provided having a plurality of microstrip elements. Conventional microstrip designs suffer from a relatively high amount of coupling due to surface wave interference between elements.
It would, therefore, be desirable to provide a multi-band antenna array arrangement, wherein respective antenna elements associated with each frequency band are selectively tunable, and wherein the frequency bands can have a relatively large frequency separation. It would be further desirable to provide a multi-band antenna array arrangement having a plurality of antenna elements that are electrically and electro-magnetically isolated from each other.
In accordance with the present invention, an antenna is provided having a substrate, a plurality of antenna elements disposed on one surface thereof, and a ground plane disposed on the other surface. A surface wave control structure is provided between antenna elements to decoupled the antenna elements from each other. The surface wave control structure has an apex that provides a sharp edge.
With this particular arrangement, antenna elements combined within an antenna array are greatly decoupled form each other. System performance, including beam pattern shape, are improved.
In accordance with another aspect of the present invention, an antenna is provided having one or more dual stacked patch assemblies, wherein each of the dual stacked patch assemblies is provided having an upper patch element and a lower patch element. One or more upper tuning structures are coupled between the upper patch element and the lower patch element. One or more lower tuning structures are coupled between the lower patch element and the ground plane. The upper and the lower tuning structures can be provided having a pre-determined orientation about the surface of the stacked patch.
With this particular arrangement, an antenna array is provided that can operate at two different frequencies wherein each frequency can be effectively and independently tuned. Furthermore, the two frequencies at which the antenna operates can be widely spaced.